1. Field of the Invention
The present invention relates to an airbag device having an airbag that is capable of being inflated and expanded by means of a gas that is supplied from a gas generator such as an inflator if a collision of a vehicle or the like occurs. In particular, the present invention relates to an airbag device that is capable of preventing twisting of a tether configured to open or close a vent hole; that is capable of making inflation and expansion speedily while restraining gas evacuation from the airbag at an initial stage at which the airbag inflates and expands to thereby set an inside of the airbag at a predetermined internal pressure; and that is capable of reliably making gas evacuation when an occupant or the like comes into contact with the airbag. In addition, the present invention relates to an airbag that is mounted in a vehicle, and that is capable of making airbag expansion that is suitable for occupant.
2. Description of the Related Art
Conventionally, in a vehicle such as an automobile, an airbag device has been installed in order to protect occupant from an impact if a vehicle collision occurs. A variety of models of airbag devices have been practically available to protect occupant at a rear passenger sheet or to protect pedestrian, or to protect occupant from an impact if a collision of a side face of a vehicle occurs or if a roll of a vehicle sideways occurs, as well as to protect a driver or an occupant at a passenger sheet. In addition, the shapes or the like of airbags are formed differently in accordance with an installation location or usage.
Many airbag devices are constructed to inflate and expand a baggy airbag by means of a high-pressure gas that is generated from a gas generator if a vehicle collision occurs, to thereby absorb and alleviate an impact caused by the collision or the like by means of the airbag. In this way, such airbags employ a construction for protecting occupant from an impact or the like.
Such airbag devices are constructed to inflate and expand an airbag momentarily by means of a high-pressure gas that is ejected from a gas generator and then appropriately release the gas inside of the airbag at a stage of constraining occupant so as to be thereby able to adjust a pressure inside the airbag and then effectively constrain occupant.
As a construction that appropriately releases the gas inside the airbag, there has been employed a construction that forms a vent hole for gas evacuation at an airbag main body. A variety of constructions of a gas evacuation portion via a vent hole has been conventionally proposed. For example, there has been proposed an airbag device for passenger seat, which is capable of restraining gas evacuation by increasing a ventilation resistance from a vent hole at an initial stage of inflation and expansion of an airbag, and that is capable of fully opening the vent hole at a later stage of the inflation and expansion (refer to Japanese Unexamined Patent Application Publication No. 2002-193058), or alternatively, an airbag device for vehicle, which is capable of effectively protecting a head of occupant even in either case where the occupant takes a seatbelt in a construction to open or close a vent hole with the use of a tether or not (refer to Japanese Unexamined Patent Application Publication No. 2009-196551) or the like.
With reference to FIG. 6, the airbag device for passenger seat, described in Japanese Unexamined Patent Application Publication No. 2002-193058, will be described as related art 1 of the present invention. As shown in FIG. 6, a part of a suspension cord main body portion 32 is pulled out from a gas evacuation opening 31 that is formed in an airbag 30 to the outside of the airbag 30 to thereby constitute a closed portion 33. At an initial stage at which the airbag 30 performs inflation and expansion, a ventilation resistance of the gas evacuation opening 31 is increased by means of the suspension cord main body portion 32 to thereby restrain gas evacuation.
In addition, at a later stage at which the inflation and expansion has been performed, the suspension cord main body portion 32 is completely pulled into the airbag 30 to be thereby able to set the gas evacuation opening 31 in a fully opened state. Then, a height dimension of the airbag 30 having performed inflation and expansion, i.e., a thickness of the airbag 30 receiving occupant is adapted to be able to be restrained by means of a suspension 34 that is pulled into the airbag 30.
This airbag device for passenger seat is capable of restraining a gas evacuation flow rate of the gas that is evacuated from the gas evacuation opening 31 in the course of inflation and expansion of the airbag 30, and is also capable of effectively utilizing an inflation gas for inflation and expansion of the airbag 30.
With reference to FIG. 7, the airbag device for vehicle, described in Japanese Unexamined Patent Application Publication 2009-196551, will be described as related art 2. As shown in FIG. 7, a tether 42 is arranged in an airbag 40 for passenger seat, and subsidiary vent holes 43 are formed at one pair of side portions 42A of the tether 42. At the forward side of each of the side portions 42A, a redundant portion 42 configured to expand by breakage of a tear seam 45 is formed. One pair of the side portions 42a is retained in a predetermined cable routing passageway along a guide 46, and the tether 42 is retained at an intermediate portion 42B so as to be disposed on a movement locus that a head of occupant who does not take a seatbelt traces.
When the airbag 40 for passenger seat has inflated and expanded, in a case where occupant has taken a seatbelt, an upper part of the body including the occupant's head is constrained by means of the seatbelt, and thus, the quantity of movement of the occupant's part to the forward side of the vehicle is limited. Therefore, the quantity of the occupant's part to get into the airbag 40 for passenger seat is reduced.
At this time, a compression force acting on the intermediate portion 42B of the tether 42 that is arranged in the airbag 40 for passenger seat becomes less than a predetermined value, failing to reach a breakage load of the tear seam 45 of the redundant portion 44. Thus, the redundant portion 44 is maintained as it is without being expanded, and in a side view, the subsidiary vent hole 41 is maintained in a state in which it is superimposed on a vent hole 41, i.e., in a state in which the vent hole 41 is opened. The gas in the airbag 40 for passenger seat is then continuously evacuated from the vent hole 41, so that an internal pressure of the airbag 40 for passenger seat can be appropriately kept.
When the airbag 40 for passenger seat has inflated and expanded, in a case where occupant has failed to take a seatbelt, the seatbelt configured to constrain an upper part of the body including the occupant's head from moving to the forward side of the vehicle has not been taken, and thus, the occupant's head moves to the forward side of the vehicle as it is. Therefore, the quantity of the occupant's head getting into the airbag 40 for passenger seat increases, and a compression force (a tension force) that acts on the intermediate portion 42B of the tether 42 becomes a predetermined value or more. The tear seam 45 having retained the redundant portion 44 then breaks.
Then, the redundant portion 44 expands, and one pair of side portions 42A at the left and right of the tether 42 is pulled to the side of the intermediate portion 42B. As a result, the subsidiary vent hole 43 that is formed in each of the side portions 42A moves to a position which is not superimposed on the vent hole 41, and the vent hole 41 of the airbag 40 for passenger seat is closed. In this manner, the internal pressure of the airbag 40 for passenger seat is maintained in a high state, and the upper part including the occupant's head can be appropriately constrained.
In the invention described in Japanese Unexamined Patent Application Publication No. 2002-193058, at the initial stage of inflation and expansion of the airbag 30, the ventilation resistance of the gas evacuation opening 31 is increased by means of a part of the suspension cord main body portion 32 that is pulled out from the gas evacuation opening 31 to the outside of the airbag 30 to be thereby able to restrain gas evacuation. In addition, at the later stage of the inflation and expansion, the suspension cord main body portion 32 is completely pulled into the airbag 30 to be thereby able to establish the gas evacuation opening 31 in a fully opened state. Moreover, the height dimension of the airbag 30 can be restrained by means of the suspension cord main body portion 32 that is pulled into the airbag 30.
However, a gas is always evacuated from the gas evacuation opening 31, and a further modification is required to further efficiently utilize the gas that is generated from the gas generator and then downsize the gas generator.
The invention described in Japanese Unexamined Patent Application Publication No. 2009-196551 is constructed so as to adjust gas evacuation with the use of the tether 42 formed in a linear shape. However, in a case where occupant has failed to take a seatbelt, when the side portions 42A are established in a distorted state, it becomes a situation that the vent hole 41 cannot be closed by means of the side portions 42A.
That is, each side portion 42A is arranged between one pair of side portions 46, and if twisting occurs between one pair of the side portions 46 or if twisting occurs at the intermediate portion 42B or the like of the tether 42, such each side portion 42A is also distorted due to the above twisting. Then, at a circumferential edge part of the vent hole 41, a site which is not covered with each of the side portions 42A is formed. If the internal pressure of the airbag 40 for passenger seat increases, a gas evacuation flow rate of the gas from the site that is not covered with each of the side portions 42A increases, an area of the side that is not covered with each of the side portions 42A increases, and the vent hole 41 is established in an opened state.
However, Japanese Unexamined Patent Application Publication No. 2009-196551 described above fails to disclose or suggest a solution or construction for prevention of a problem with twisting of the side portions 42A.
The present invention has been made to solve the conventional problem described above, and it is an object of the present invention to provide an airbag device, with a simple construction, that is capable of restraining a rectification cloth configured to switch a vent hole to an opened or closed state so as not to be distorted; that is capable of performing speedy inflation and expansion while restraining gas evacuation from an airbag at an initial stage at which the airbag inflates and expands; that is capable of reliably performing gas evacuation if occupant or the like comes into contact with the airbag partway of expansion and inflation; that is capable of stopping gas evacuation and maintaining an internal pressure of the airbag in a predetermined internal pressure state when the internal pressure of the airbag has reached at the predetermined pressure; and that is capable of reliably making gas evacuation if occupant or the like comes into contact with an airbag that has reached a predetermined internal pressure.
In addition, in order to alleviate an impact to occupant in a case of vehicle collision, a variety of airbags are known, and their mounting locations also increase. A variety of airbags are applied to many vehicles, including an airbag configured to expand forward of occupants taking a driver seat and a passenger seat in order to cope with collision from a front side or a side cushion-type airbag or a curtain-shaped airbag partially covering side portions of a vehicle in order to cope with collision of another vehicle with a side face or roll of vehicle sideways.
With the spread of such airbags, their effectiveness is verified in a very large number of actuation cases (collision cases), whereas a variety of attempts are made as to a modification for providing a protection that is further preferable as well.
As the related art according to the present invention, there exists an airbag that is inflated and expanded by means of a gas supplied from an inflator into a baggy bag main body, the airbag including: a variable vent hole in which a gas distribution state inside and outside of the bag main body is changed in accordance with an expansion state of the bag main body; and a distribution state change means for changing a gas distribution state in the variable vent hole, wherein the bag main body is expanded in a stepwise manner in a plurality of directions, the distribution state change means is established in an allowable state allowing for gas distribution in an initial expansion direction at an initial stage of inflation and expansion of the bag main body, and is configured to selectively set the allowable state and a restraint state restraining gas distribution inside and outside of the bag main body via the variable vent hole, at a subsequent stage of expansion that is subsequent to the initial stage of expansion, and that is in an expansion direction different from the initial expansion state (for example, refer to Japanese Unexamined Patent Application No. 2005-14861).
In Japanese Unexamined Patent Application No. 2005-14861 that is the related art, one linear base cloth valve is used to open or close a gas evacuation hole for evacuating a redundant gas for airbag inflation and expansion suitable for protection of occupant.
However, in the linear base cloth valve, the base cloth valve is thinned due to breakage or twisting of the base cloth valve at the time of the maximum inflation and expansion of an airbag, the gas evacuation hole is not well closed, and there is a possibility that suitable airbag expansion cannot be performed.
Therefore, there is a need to contrive a preferred folding method or a means for smoothing movement of the base cloth valve, airbag research and development or manufacturing stage becomes complicated, and there has been a problem associated with a higher cost.
Accordingly, it is an object of the present invention to provide an airbag that is capable of stably and easily making suitable airbag expansion that is a solution of the problem described above.